Biology 3 - Excahnge and Transport

  • Created by: Alice
  • Created on: 01-04-15 13:27

Diffusion and Active Transport

Dissolved substances can more into or out of cells by diffustion or active transport.
Water moves into and out of cells by a special type of diffusion called osmosis.

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Keeping the body hydrated is important for human health.
Water lost in sweat during exercise must be replaced.

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Sports Drinks

Sports drinks contatin water for hydration, but also glucose for energy and ions to keep the body healthy.

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Active Transport

Active Transport moves substances across cell membranes against a concentration gradient.
This require energy and a protein carrier.

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Diffusion adaptions

As organisms get bigger their surface-area-to-volume ratio gets smaller.
This makes diffusion inefficient.
To solve the problem they develop special exchange surfaces.

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Exchange surfaces

All exchange surfaces are thin, have a large surface area, and have systems to maintain a concentration gradient.

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The villus is the site of absorption in the small intestine, and is efficiently designed.

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Gas exchange vs. Breathing

The lungs are the organs of gas exchange in humans.
Breating is the process which brings air in and out of the lungs.

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Transpiration is the loss of water from the leaves of the plant.
Water leaves the plant through tiny pores called stomata on the under surface of the leaf.

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Rate of transpiration

The rate of transpiration can be measured by a potometer, and can be affected by a number of environmental factors.

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Large organisms

A second problem for larger organisms is that they require a transport system to move substances around the body.

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Circulatory System

Humans have a circulatory system that involves the heart, blood, and blood vessels.

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The heart

The heart is a muscular pump that pushes the blood around the body. 
Blood passes through the heart twice in one cycle of the body; it is a double circulatory system.

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The blood is the fluid that transports substances.
It is composed of a liquid called plasma, and cells - red cells, white cells, and platelets - each with their own function.

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Vessels - viens, capillaries and arteries

The blood is circulated in vessels: arteries take blood away from the heart, capillaries take blood through the tissues, where exchange occurs, and veins take blood back to the heart.

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Technology - Artifical hearts and blood.

Technology has developed artificial blood for use in transfusions, and stents to open blocked vessels.
Artificial hearts or valves can be used to replace damaged ones.

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Plant transport - Xylem and Phloem

Plants also transport substances.
The xylem transports water from roots to the leaves, whilst the phloem transports sugars from the leaf to other parts of the plant.

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